The preceding table is deduced from experiments made by the breaking of ropes of various sizes, with one of their ends attached to a frame suspended to a strong iron beam, moving on steel pivots; to the other end of which beam weights were progressively suspended until the ropes broke. By these means the patent shroud-laid ropes, made of Petersburg clean hemp, were found almost uniformly to break with a stress fluctuating between 6 and 74 cwt. per inch of their girt, in inches squared; thus a patent rope of 5 inches girt would, on an average, require 175 cwt. to break it. Common made ropes of the same hemp, and of 25 threads in each strand, broke with 5 cwt. per inch, and kept a progressive decrease, so as with about 130 threads to fall off to 4 cwt. per inch. The threads were of the common size; and the latter rope rather exceeded 8 inches girt. When strands were broken separately, the disparity between those of the common and the improved methods was much greater than in the ropes themselves. These experiments being made in the manner before stated, no deduction from the strength given has to be made for friction, which otherwise would have been requisite.

The duration of patent ropes in drawing coals, &c. from mines, or for other purposes where they are subject to be worn, is still greater than their superiority of strength over common rope; because, when the outside shell or coat of yarns of the latter is much worn, the whole of it gives way; the rope then lengthens suitably to the next coat, loses its form, and becomes unfit for use.

Whale lines are generally of 21 inches girt and 28 threads to the strand, and made from finely dressed hemp of the best quality; these lines have been found to break under resistances of between 25 and 32 cwt. equal to between 5 and 6 cwt. per inch rope; whilst lines made from the same yarns, patent laid, and only 2 inches girt, have carried considerably above 2 tons; so that the latter are much stronger and lighter, and, of course worthy of general preference.

To find the Tonnage of a Vessel by the United States' Measurement.

The length is taken from the fore part of the main stem to the after part of the stern-post; the beam is measured at the extreme breadth to the outside of the bends; three fifths of this beam is taken off the length, before the calculation is made; for a double decked vessel half the breadth of beam is called the depth of hold; and for a single decked vessel it is the same, except that the hold is measured at the fore part of the main hatchway, from the deck down to the ceiling along side of the kelson.

To proceed on in the calculation, after all the allowances have been made, the length must be multiplied by the breadth, and that product by the depth of hold; then divide the last product by 95, and the quotient will give the tonnage required.

Formerly the British divided by 94 for merchant vessels, and for ships of war by 100; but I have been informed that they now divide by 100 both for ships of war and merchantmen, which is the reason that they make our ships tonnage less than we do.

The ship carpenter's tonnage in Philadelphia differs from the United States' measurement. A rule staff is laid under the keel, projecting forward; a line is plumbed from the upper part of the fore part of the stem to the rule staff; the keel is measured from its after part to the plumb line, along and including the rule staff, this is called the length of keel, straight rabbit. The beam is measured from skin to skin, on the inside; three fifths of this beam is taken off the keel, straight rabbit, for the length and the calculation, in other respects, is the same as United States' measurement; so that the carpenters' tonnage in Philadelphia will be less, according to the rake of the stern-post, &c.

The dead rise of a vessel is found by having a staff half the beam, from skin to skin, at the extreme breadth, which staff is laid even across on the ceiling, at the fore part of the main hatchway. One of the limber boards being taken up, a line is let fall from the staff to the skin, along side of the kelson, and what it measures is the vessel's dead rise; so that in order to know how sharp a vessel is, it is customary to ask how much dead rise she has.

Examples in Calculating Tonnage, United States' Measurement. Length, after three fifths of the beam is deducted, 102 feet. Beam,

Depth of hold, being half beam,

30

3060

15

15360

3060

95)45900(483

380

790

760

300

285

15

Tonnage, 483 tons and 15 ninety-fifths.

Suppose a ship's length, after three fifths of beam being taken off, is 102 feet 6 inches; breadth of beam 30 feet 6 inches ; depth of hold half the breadth of beam, which will be 15 feet 3 inches.

What Vessels of different Classes will carry in Proportion to their Measurement.

A full built ship of 300 tons will hold 50 per cent. above her tonnage; that is, she will carry 450 tons measurement goods, calculating 40 cubic or solid feet to the ton.

A ship of 300 tons, if very sharp built, will not hold more than 390 tons measurement goods. They will hold more in proportion as they are less sharp built.

A ship of 400 tons, full built, will hold 60 per cent. above her tonnage; but if she be sharp built, she will hold about 40 per cent. on her tonnage of measurement goods.

A ship of 500 tons, full built, will hold 75 per cent. above her tonnage.

A ship of 650 tons, sharp built, will hold 50 per cent. above

her tonnage.

A ship of 600 tons, full built, will hold 75 per cent. on her tonnage.

A ship of 600 tons, sharp built, will hold 50 per cent. above her tonnage; so that the larger the vessel the more she will hold above her tonnage; as a ship of 1200 tons, full built, will hold from 90 to 100 per cent. on her tonnage; and a ship of 1200 tons, sharp built, may hold from 60 to 70 per cent. above her tonnage; while a vessel of 200 tonnage, sharp built, perhaps will not hold equal to her tonnage.

THE

BEST METHOD

TO BE PURSUED BY MERCHANT SHIPS TO ESCAPE FROM AN ENEMY OF SUPERIOR FORCE.

Though a merchant ship be well supplied and fitted for a close fight, yet the commander is not obliged to fight a privateer, if he can with safety shun her: and if he should be chased, he ought to embrace every advantage that can be taken by wind or tide.

The enemy being to windward, it is best for a three masted vessel to sail quartering.

The ship chased, having the liberty of chusing her course, may steer as she pleases; but the commander, in making his choice, is to pitch upon that which answers best; which is to prolong the time, that the night may cover his escape, or he may meet with a friend to secure him. Sailing quartering is found to be the swiftest motion a ship can make through the water, when all sails draw; and the enemy is obliged to go right before the wind to come up with the chase; then he can have only part of his sails drawing, while the chase has all hers, and if the enemy sails quartering also, he must keep a parallel course with the chase, or rather his course will be inclined to windward, because his yards (as in most privateers) are squarer than merchantmen. He must bring the wind more points on the quarter, that all sails may draw ; and if he pursues this method, he must at last bear down before the wind into her wake.

The conduct to be used by Merchant Ships to get to Windward.

If the enemy be directly to windward, the chase must then. first sail quartering. If the enemy bear down before the wind, then she may gradually bring the wind forward till it is upon the beam and if the enemy still bear for your wake, luff as he gains it, till you are hauled sharp and he in your wake; then